Why it matters: Fox initially rejected a higher bid from Comcast, fearing regulatory hurdles with a vertical merger, according to SEC filings. But if AT&T's merger with Time Warner is allowed, Fox may have incentive to take Comcast's higher bid, leaving Disney in the dust.

Comcast says that while no final decision has been made, "at this point the work to finance the all-cash offer and make the key regulatory filings is well advanced."

It wouldn't be shocking if Fox ditched Mickey Mouse for the telecom giant, although CNBC reported Tuesday that Fox is closing in on a shareholder vote over Disney's $52 billion bid for Fox's media assets.

While Fox executives have made it clear that Disney is its preferred merger partner, the company will need money to pilot its new separate sports and news network, and Comcast's bid is reportedly higher than Disney's.

Between the lines: A reported rivalry between Comcast CEO Brian Roberts and Disney CEO Bob Iger could also be playing into bidding wars.